The two operators have agreed to build the next phase of their 4G networks and both companies will together invest £1 billion to complete LTE infrastructure.
Sharing mast infrastructure and transmission costs between the masts and the main national networks is included in the deal.
The agreement will accelerate the operators 4G roll-out plans and should help both companies cut costs.
EE expects to invest a total of £1.4 billion into its 4G network while Three has announced that it will invest £500 million in the next three years.
EE expects its 4G network to reach 98% of the population by the end of 2014 and Three intends to reach the same target one year later.
